AQA Physics A - PHYA5 (18/06/12) - Exam thread

Thanks for your help on relativity people, however despite thinking of my cognition abilities to be of at least average I can't wrap my head around it really, I think I do understand why time gets shorter and distance must get shorter though for a fast moving object

To be fair, special relativity is a bit of a mind boggler.

As long as you understand that as speed approaches speed of light, you get heavier, time is slower, and distance is shorter; you shouldn't have much of a problem tomorrow! :smile:

Reply 781

username570910

2

Original post by TheRenaissanceMan

These notes are so decent ! Cheers mate

No problem, glad to help! :smile:

Reply 782

don'tTRIP.

2

Some confusion with regards the inverse square law formula; in some mark schemes it's listed with x1 as the numerator, but others it's the denominator? Such inconsistency :emo:

Reply 783

robthefool

12

Original post by albus

The old Unit 2

Thanks

Reply 784

aim28

Original post by don'tTRIP.

Some confusion with regards the inverse square law formula; in some mark schemes it's listed with x1 as the numerator, but others it's the denominator? Such inconsistency :emo:

Isn't it just I=k/x2 (that's supposed to be x squared sorry :/)

Reply 785

Red Richie

15

Original post by albus

For Astro, 6 markers might be on CCDs or stars in binary systems.

its not going to be an experiment sort of question is it?

is it just going to ask us to talk about CCDs and explain them?

Reply 786

Z.93

2

I know the exam is tomorrow lol, but this website is WELL WORTH a look for last minute revision...worked wonders for me!

http://www.antonine-education.co.uk

good luck!!

Reply 787

Red Richie

15

btw, anyone doing astrophysics, do we need to memorise/know the star spectral classes?

Reply 788

Machoo

Original post by Red Richie

its not going to be an experiment sort of question is it?

is it just going to ask us to talk about CCDs and explain them?

It could be anything, but an experiment is very unlikely.

Reply 789

username512063

1

I hate it when the mark schemes use rounded values to produce answers, rather than the originals. Losing marks for using the exact, more accurate values, is absolutely absurd.

Reply 790

her17

1

Original post by Red Richie

btw, anyone doing astrophysics, do we need to memorise/know the star spectral classes?

i'm not sure if it's actually on the specification, but my teacher made us learn them

Reply 791

ksryiovulna356

Original post by don'tTRIP.

Some confusion with regards the inverse square law formula; in some mark schemes it's listed with x1 as the numerator, but others it's the denominator? Such inconsistency :emo:

If you mean the "Before and after" questions, I just derive in the exam.

I1=K/(X1^2)
I2=K/(X2^2)

K=I1X1^2
K=I2X2^2

I1X1^2=I2X2^2
I1/I2=X2^2/X1^2

As for the incosistency, it depends on what's defined as X1. It varies from question to question. Also, this equation can be flipped on both sides.

Reply 792

her17

1

how do i know how many significant figures to leave my answer at? in the marks schemes it's sometime given to two and sometimes given to three, and I can't identify a pattern :s

Reply 793

ksryiovulna356

Original post by Red Richie

btw, anyone doing astrophysics, do we need to memorise/know the star spectral classes?

For AQA? Yes. I don't know how much detail we need. Whether it's just the orders or the actualy temperatures as well as the elements fused and absorbtion lines.

Reply 794

Elliott.griffiths

Original post by her17

i'm not sure if it's actually on the specification, but my teacher made us learn them

Yes you do, and what properties each class shows.
OBAFGKM

I suggest reading the Spec. The most common question is why Hydrogen Balmer absorption lines are produced.

(edited 11 years ago)

Reply 795

ksryiovulna356

Original post by her17

how do i know how many significant figures to leave my answer at? in the marks schemes it's sometime given to two and sometimes given to three, and I can't identify a pattern :s

Either is accepted. If you look at the front of the mark scheme it should say something along the lines of "Accept all answers to 2 or 3SF unless the question states otherwise".

Reply 796

albus

2

Original post by Red Richie

its not going to be an experiment sort of question is it?

is it just going to ask us to talk about CCDs and explain them?

If its a CCD question, I'd write something like this:

A CCD is silicon chip divided into picture elements (pixels).
Incident photons cause electrons to be released.
The number of electrons liberated is proportional to the intensity of the light.
These electrons are trapped in ‘potential wells’ in the CCD.
An electron pattern is built up which is identical to the image formed on the CCD.
When exposure is complete, the charge is processed to give an image.
Quantum efficiency of pixel > 70%.

Reply 797

sconter

11

Original post by her17

how do i know how many significant figures to leave my answer at? in the marks schemes it's sometime given to two and sometimes given to three, and I can't identify a pattern :s

to whatever sig fig the information u r given

if you are told something is 65cm apart
then 2 sig fig

if you are told 235mm
then ur answer should be to the same sig fig as that

also if you measuring something, it is to the accuracy of the thing you are using.

Reply 798

ksryiovulna356

Does anyone know the definitions of a black hole and event horizon? I mean, I know what they are, but what do you have to say to score the marks?

Reply 799

username570910

2

Original post by albus

If its a CCD question, I'd write something like this:

A CCD is silicon chip divided into picture elements (pixels).
Incident photons cause electrons to be released.
The number of electrons liberated is proportional to the intensity of the light.
These electrons are trapped in ‘potential wells’ in the CCD.
An electron pattern is built up which is identical to the image formed on the CCD.
When exposure is complete, the charge is processed to give an image.
Quantum efficiency of pixel > 70%.

I don't think it will be on CCDs because there was a 3 marker on them in June 10. The examiners report says "In part (c), the question on the CCD was a fairly regular feature of the legacy paper, and there was some evidence to suggest that many candidates simply learned the mark scheme from previous exams." So I doubt they'd give us a 6 marker on them, as much as i'd like it.

AQA Physics A - PHYA5 (18/06/12) - Exam thread

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